{"title":"Control Randomisation Approach for Policy Gradient and Application to Reinforcement Learning in Optimal Switching","authors":"Robert Denkert, Huyên Pham, Xavier Warin","doi":"10.1007/s00245-024-10207-5","DOIUrl":"10.1007/s00245-024-10207-5","url":null,"abstract":"<div><p>We propose a comprehensive framework for policy gradient methods tailored to continuous time reinforcement learning. This is based on the connection between stochastic control problems and randomised problems, enabling applications across various classes of Markovian continuous time control problems, beyond diffusion models, including e.g. regular, impulse and optimal stopping/switching problems. By utilizing change of measure in the control randomisation technique, we derive a new policy gradient representation for these randomised problems, featuring parametrised intensity policies. We further develop actor-critic algorithms specifically designed to address general Markovian stochastic control issues. Our framework is demonstrated through its application to optimal switching problems, with two numerical case studies in the energy sector focusing on real options.</p></div>","PeriodicalId":55566,"journal":{"name":"Applied Mathematics and Optimization","volume":"91 1","pages":""},"PeriodicalIF":1.6,"publicationDate":"2024-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142826391","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"CAT(0) and cubulated Shephard groups","authors":"Katherine M. Goldman","doi":"10.1112/jlms.70050","DOIUrl":"https://doi.org/10.1112/jlms.70050","url":null,"abstract":"<p>Shephard groups are common generalizations of Coxeter groups, Artin groups, and graph products of cyclic groups. Their definition is similar to that of a Coxeter group, but generators may have arbitrary order rather than strictly order 2. We extend a well-known result that Coxeter groups are <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>CAT</mi>\u0000 <mo>(</mo>\u0000 <mn>0</mn>\u0000 <mo>)</mo>\u0000 </mrow>\u0000 <annotation>$mathrm{CAT}(0)$</annotation>\u0000 </semantics></math> to a class of Shephard groups that have ‘enough’ finite parabolic subgroups. We also show that in this setting, if the associated Coxeter group is type (FC), then the Shephard group acts properly and cocompactly on a <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>CAT</mi>\u0000 <mo>(</mo>\u0000 <mn>0</mn>\u0000 <mo>)</mo>\u0000 </mrow>\u0000 <annotation>$mathrm{CAT}(0)$</annotation>\u0000 </semantics></math> cube complex. As part of our proof of the former result, we introduce a new criteria for a complex made of <span></span><math>\u0000 <semantics>\u0000 <msub>\u0000 <mi>A</mi>\u0000 <mn>3</mn>\u0000 </msub>\u0000 <annotation>$A_3$</annotation>\u0000 </semantics></math> simplices to be <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>CAT</mi>\u0000 <mo>(</mo>\u0000 <mn>1</mn>\u0000 <mo>)</mo>\u0000 </mrow>\u0000 <annotation>$mathrm{CAT}(1)$</annotation>\u0000 </semantics></math>.</p>","PeriodicalId":49989,"journal":{"name":"Journal of the London Mathematical Society-Second Series","volume":"111 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2024-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1112/jlms.70050","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142861574","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Spectral influence in networks: an application to input-output analysis","authors":"Nizar Riane","doi":"10.1007/s10878-024-01244-5","DOIUrl":"https://doi.org/10.1007/s10878-024-01244-5","url":null,"abstract":"<p>This paper introduces the concepts of spectral influence and spectral cyclicality, both derived from the largest eigenvalue of a graph’s adjacency matrix. These two novel centrality measures capture both diffusion and interdependence from a local and global perspective respectively. We propose a new clustering algorithm that identifies communities with high cyclicality and interdependence, allowing for overlaps. To illustrate our method, we apply it to input-output analysis within the context of the Moroccan economy.</p>","PeriodicalId":50231,"journal":{"name":"Journal of Combinatorial Optimization","volume":"85 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2024-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142832114","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Relating code equivalence to other isomorphism problems","authors":"Huck Bennett, Kaung Myat Htay Win","doi":"10.1007/s10623-024-01542-3","DOIUrl":"https://doi.org/10.1007/s10623-024-01542-3","url":null,"abstract":"<p>We study the complexity of the <i>Code Equivalence Problem</i> on linear error-correcting codes by relating its variants to isomorphism problems on other discrete structures—graphs, lattices, and matroids. Our main results are a fine-grained reduction from the Graph Isomorphism Problem to the Linear Code Equivalence Problem over any field <span>(mathbb {F})</span>, and a reduction from the Linear Code Equivalence Problem over any field <span>(mathbb {F}_p)</span> of prime, polynomially bounded order <i>p</i> to the Lattice Isomorphism Problem. Both of these reductions are simple and natural. We also give reductions between variants of the Code Equivalence Problem, and study the relationship between isomorphism problems on codes and linear matroids.</p>","PeriodicalId":11130,"journal":{"name":"Designs, Codes and Cryptography","volume":"2021 1","pages":""},"PeriodicalIF":1.6,"publicationDate":"2024-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142832039","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"A Fourier multiplier theorem on anisotropic Hardy spaces associated with ball quasi-Banach function spaces","authors":"Xianjie Yan, Hongchao Jia, Dachun Yang","doi":"10.1007/s43034-024-00396-z","DOIUrl":"10.1007/s43034-024-00396-z","url":null,"abstract":"<div><p>Let <i>A</i> be a general expansive matrix. Let <i>X</i> be a ball quasi-Banach function space on <span>(mathbb {R}^n)</span>, which supports both a Fefferman–Stein vector-valued maximal inequality and the boundedness of the powered Hardy–Littlewood maximal operator on its associate space. The authors first establish the boundedness of convolutional anisotropic Calderón–Zygmund operators on the Hardy space <span>(H_X^A(mathbb {R}^n))</span>. As an application, the authors also obtain the boundedness of Fourier multipliers satisfying anisotropic Mihlin conditions on <span>(H_X^A(mathbb {R}^n))</span>. All these results have a wide range of applications; in particular, when they are applied to Lebesgue spaces, all these results reduce back to the known best results and, even when they are applied to Lorentz spaces, variable Lebesgue spaces, Orlicz spaces, Orlicz-slice spaces, and local generalized Herz spaces, the obtained results are also new.</p></div>","PeriodicalId":48858,"journal":{"name":"Annals of Functional Analysis","volume":"16 1","pages":""},"PeriodicalIF":1.2,"publicationDate":"2024-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142826150","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Multi-indice \u0000 \u0000 B\u0000 $B$\u0000 -series","authors":"Yvain Bruned, Kurusch Ebrahimi-Fard, Yingtong Hou","doi":"10.1112/jlms.70049","DOIUrl":"https://doi.org/10.1112/jlms.70049","url":null,"abstract":"<p>We propose a novel way to study numerical methods for ordinary differential equations in one dimension via the notion of multi-indice. The main idea is to replace rooted trees in Butcher's <span></span><math>\u0000 <semantics>\u0000 <mi>B</mi>\u0000 <annotation>$B$</annotation>\u0000 </semantics></math>-series by multi-indices. The latter were introduced recently in the context of describing solutions of singular stochastic partial differential equations. The combinatorial shift away from rooted trees allows for a compressed description of numerical schemes. Furthermore, such multi-indices <span></span><math>\u0000 <semantics>\u0000 <mi>B</mi>\u0000 <annotation>$B$</annotation>\u0000 </semantics></math>-series uniquely characterize the Taylor expansion of 1-dimensional local and affine equivariant maps.</p>","PeriodicalId":49989,"journal":{"name":"Journal of the London Mathematical Society-Second Series","volume":"111 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2024-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142861491","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}